Photographic recording material

ABSTRACT

A photographic recording material having a support which has at least one light-sensitive silver halide emulsion layer on one side and at least one layer or layer region which comprises a laser additive on the other side (the reverse side) is outstandingly suitable for printing with a laser coder.

This application is a continuation-in-part-of application Ser. No.09/059,408, filed Apr. 14, 1998, now abandoned.

This invention relates to a photographic recording material having asupport which has at least one light-sensitive silver halide emulsionlayer on one side and at least one layer or layer region which can beprinted on the other side (the reverse side). The support is preferablya paper material which is coated on both sides with polyethylene (PE).

There is an interest in the printing of information on the reverse sideof photographic papers, e.g. the company logo of the paper manufactureror of the processor, or text and figures which the manufacturer orprocessor applies at his own wish or at the wish of the customer.

The applied printed image should be of very high quality. As far aspossible, the printing operation should proceed at a speed which iscompletely synchronous with the speed of image processing. The processshould be environmentally friendly, should exhibit a flexibility whichis as high as possible, and should be economical.

The reverse side of photographic paper is usually provided with anantistatic layer, which consists of a polyelectrolyte as an antistaticadditive, a binder system and of additives such as hardeners and wettingagents.

Reverse side coatings of this type are designed so that they can beprinted with printers such as inking ribbon printers, thermal printersand inkjet printers which are used for the image processing ofphotographic papers. The applied printed image does not satisfy therequirements. Particularly mechanical factors like abrasion can resultin a reduction of print quality, however. Therefore, there is still aneed for improvement here.

What is required is a durable, solvent-resistant printed image which iswipe- and scratch-resistant. In addition, high print quality, printingspeed and flexibility, and a high extent of environmental compatibilityshould be ensured.

SUMMARY OF THE INVENTION

It has now been found that these objects can be achieved if the reverseside contains a laser additive in at least one layer or one layer regionand a laser printer is used for printing.

The present invention therefore relates to a photographic material ofthe type cited at the outset, which contains an effective amount of alaser additive in the PE laminate on the reverse side or in the internalmaterial of the support also.

DETAILED DESCRIPTION OF THE INVENTION

These laser additives are functional pigments which triggercontrast-increasing reactions in plastics during laser bombardment.Colour changes of this type can arise due to a dark coloration of thepolymer matrix in the surroundings of the pigment which results frompartial carbonisation, wherein it is principally only the pigmentparticles near the surface which are involved, so that more progressivedamage, to the substrate, can be ruled out. A colour change can also becaused, however, by a discoloration within the pigment itself Finally, avisual change may also be the result of bubble formation at the surface.This is the situation in particular for plastics which exhibit notendency or only a slight tendency towards carbonisation. In the lattercase, a light to white marking is formed. Depending on the plastic, thepigment and the type of laser, markings are possible which range fromwhite via grey to black.

Laser additives (laser-markable plastics) are known from EP 750 012, WO95/30 546 and EP 718 378, for example.

Examples of laser additives which are particularly suitable are thosewhich are marketed by the Merck company, of Darmstadt, under the tradename Iriodin® LS pigments (LS=laser-sensitive). Moreover, it is alsopossible to obtain certain gloss effects by admixing these with effectpigments, such as Iriodin® pearl gloss pigments.

Incorporation into the PE laminate layer can be effected by directaddition to a compound. The additives may also be added as a masterbatch with an additive content of from 5 to 50% by weight, for example.Even small added amounts of the pigment active ingredient are sufficientto achieve a contrast effect due to the laser. As a band width, a rangefrom 0.1 to 10.0% by weight can be added. The addition does not have asignificant effect on the material properties of the layer matrix.

A prerequisite for laser coding is that a laser is used, the radiationof which has a wavelength range outside the photographic sensitivity.CO₂ lasers with a wavelength in the μm range and YAG lasers with awavelength above 1000 nm are particularly suitable.

Lasers of this type have a high output capacity. They make it possibleto achieve high printing speeds and sharp-edged images, even forsmall-scale images. The inscription may be produced via pre-alignedmasks, for example, and the inscription may also be produced on movingtypesetting copies, in the present case on the reverse side, oftravelling photographic strips. A variable printed image can also beproduced by deflecting the laser beam in the x-y direction. The inputcan be programmed via computer programs and thus facilitates a highdegree of flexibility.

A detailed summary of the process described here is given in a brochureof the Merck company on the topic of Iriodin® LS for the laser-markingof plastics.

EXAMPLE

Iriodin® LS 825, manufactured by Merck, was incorporated as a masterbatch in the PE laminate on the reverse side of a colour negative papercomprising paper as a support which was coated on both sides with PE.The master batch contained 10% by weight of Iriodin® LS 825 and the PElaminate contained 6% of the master batch. The incorporated product is anearly transparent pigment, so that the visual white impression of thereverse side of the photographic material remained substantiallyunchanged. The characters were marked with a Nd: YAG laser. Asharp-edged, easily legible print image with a medium grey gradation wasobtained. No damage occurred to the PE laminate.

We claim:
 1. A process for printing the reverse side of a photographicrecording material, characterised in that a photographic recordingmaterial having a support which has one light-sensitive silver halideemulsion layer on one side and at least one layer or layer region whichcomprises a laser additive on the other side (the reverse side) isprinted with a laser coder based on a YAG laser.